Self-cleaning coating composition, self-cleaning coating and preparation method thereof

Abstract

This invention provides a self-cleaning coating composition, a self-cleaning coating, and a method for preparing the same. The self-cleaning coating composition comprises a carbon nanotube dispersion, a first nano-silica dispersion, a second nano-silica dispersion, and hexamethyldisilazane; wherein the first nano-silica dispersion comprises first nano-silica, the second nano-silica dispersion comprises second nano-silica, and the average particle size difference between the first and second nano-silica is 40–60 nm. This invention utilizes two different hydrophobic nano-silica particles with an average particle size difference within this range to construct a suitable nano-roughness, while simultaneously increasing the porosity of the coating by adding a small amount of nanotubes. The roughness construction enhances the self-cleaning performance of the coating, while the micropore construction reduces light reflection, improves the light transmittance of the self-cleaning coating, and provides excellent self-cleaning function.

Description

Technical Field

[0001] This invention relates to the field of photochemical reaction technology, and more specifically, to a self-cleaning coating composition, a self-cleaning coating, and a method for preparing the same. Background Technology

[0002] The photoelectric conversion efficiency of photovoltaic (PV) power generation has approached the theoretical conversion value. However, external factors such as the environment are increasingly impacting the power generation efficiency of PV modules and the power output of power plants. Among these factors, the deposition of dust and dirt on the glass surface can cause a decrease in solar cell efficiency of over 50%. The impact of dust accumulation on module power output has become a key research focus for improving the quality and efficiency of PV power plants. Applying a superhydrophobic, highly transparent, self-cleaning coating to the surface of the solar cell cover glass can reduce cleaning frequency, improve cleaning efficiency, reduce water consumption, extend the lifespan of PV modules, and increase PV power generation efficiency.

[0003] However, superhydrophobic, highly transparent, and self-cleaning coatings have not yet been widely adopted in photovoltaic power plants, mainly due to the following three factors: (1) The microstructure of the self-cleaning coating is damaged under the harsh natural environment of photovoltaic power plants, and its adhesion to the glass substrate is poor, resulting in poor durability of the film material; (2) The high roughness required to prepare the superhydrophobic coating leads to light scattering, thereby reducing the light transmittance of the cover glass and affecting the power generation efficiency of the solar cell; (3) The coating's construction process is complex and has high environmental requirements, limiting its large-scale application. Therefore, developing a low-cost, room-temperature moldable, and sprayable superhydrophobic, highly transparent, and self-cleaning coating remains a challenge. Summary of the Invention

[0004] The main objective of this invention is to provide a self-cleaning coating composition, a self-cleaning coating, and a method for preparing the same, in order to solve the problems of poor durability, poor self-cleaning properties, and low light transmittance to the cover glass of photovoltaic modules, which lead to low service life and low photovoltaic power generation efficiency of traditional superhydrophobic and highly transparent self-cleaning coatings in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a self-cleaning coating composition is provided, the self-cleaning coating composition comprising a carbon nanotube dispersion, a first nano-silica dispersion, a second nano-silica dispersion, and hexamethyldisilazane; wherein the first nano-silica dispersion comprises first nano-silica, the second nano-silica dispersion comprises second nano-silica, and the average particle size difference between the first nano-silica and the second nano-silica is 40-60 nm.

[0006] Furthermore, the mass ratio of the first nano-silica to the second nano-silica is 1:2 to 2:1.

[0007] Furthermore, the mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 5 to 100:1, and / or the mass ratio of the first nano-silica and the second nano-silica to hexamethyldisilazane is 0.1 to 2.5:1.

[0008] Furthermore, the above-mentioned carbon nanotube dispersion includes carbon nanotubes and a first dispersant; wherein the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, preferably with a diameter of 2-30 nm; and / or the first dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0009] Furthermore, the aforementioned first nano-silica dispersion also includes a second dispersant, wherein the average particle size of the first nano-silica is 5-50 nm; and / or the second dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0010] Furthermore, the above-mentioned second nano-silica dispersion also includes a third dispersant, wherein the average particle size of the second nano-silica is 51-100 nm; and / or the third dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0011] According to another aspect of the present invention, a method for preparing a self-cleaning coating is provided, the method comprising step S1, mixing a self-cleaning coating composition by stirring to obtain a self-cleaning coating; and step S2, spraying the self-cleaning coating onto the surface of a substrate and drying it to obtain a self-cleaning coating; wherein the self-cleaning coating composition is the aforementioned self-cleaning coating composition.

[0012] Further, in step S1 above, the stirring and mixing temperature is 20-30℃, and / or the stirring and mixing time is 0.5-48h, and / or the stirring and mixing rate is 300-1000rpm; preferably, step S1 also includes the preparation process of the first nano-silica dispersion and the second nano-silica dispersion, wherein the preparation process of the first nano-silica dispersion includes: mixing the first silicon source and the second dispersant to obtain a first mixture; heating the first mixture to 25-40℃ and then adding ammonia water dropwise while stirring for 1-3h; after the ammonia water is completely added, continuing to stir for 12-24h to obtain the second nano-silica dispersion; wherein the volume ratio of the first silicon source to the second dispersant is 0.025-0.25:1; and the volume ratio of ammonia water to the first silicon source is 0.5-1.5:1; The preparation method of the second nano-silica dispersion includes: mixing a second silicon source with a third dispersant to obtain a second mixture; heating the second mixture to 41-60°C and then adding ammonia water dropwise while stirring for 1-3 hours; after the ammonia water is completely added, continuing to stir for 12-24 hours to obtain the second nano-silica dispersion; wherein the volume ratio of the second silicon source to the third dispersant is 0.025-0.25:1; the volume ratio of ammonia water to the second silicon source is 1.6-4:1; preferably, the first silicon source and the second silicon source are each independently selected from any one or more of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and methyltriethoxysilane (MTES); preferably, the total volume ratio of the first silicon source and the second silicon source to the volume ratio of hexamethyldisilazane is 0.1-10:1.

[0013] Furthermore, in step S2 above, the drying temperature is 20-30°C, and / or the drying time is 3-48 hours; and / or the spraying pressure is 0.5-1 MPa, the spraying distance between the self-cleaning coating outlet and the substrate is 5-20 cm, preferably 8-15 cm, and the spraying time is preferably 1-3 seconds.

[0014] According to another aspect of the present invention, a self-cleaning coating is provided, which is prepared by the aforementioned preparation method.

[0015] Applying the technical solution of this invention, the self-cleaning coating composition provided by this invention utilizes two types of hydrophobic nano-silica with different particle sizes to construct a suitable nano-roughness, while simultaneously increasing the porosity of the coating by adding a small amount of nanotubes. The roughness construction enhances the self-cleaning performance of the coating, while the micropore construction reduces light reflection and improves the light transmittance of the self-cleaning coating. For example, the self-cleaning coating of this invention achieves a maximum light transmittance of 90%, a water contact angle of up to 161°, and a roll-off angle of less than or equal to 15°. Furthermore, the self-cleaning coating composition of this application uses inexpensive raw materials, is fluorine-free, and can be applied by spraying and dried at room temperature to form a film. The resulting coating has high transparency and excellent self-cleaning function, meeting the requirements for large-scale outdoor construction. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A photograph of a water contact angle test of a superhydrophobic self-cleaning coating provided according to Embodiment 5 of the present invention is shown, wherein the water contact angle is 161°. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] As analyzed in the background section of this application, traditional superhydrophobic and highly transparent self-cleaning coatings in the prior art suffer from problems such as poor durability, poor self-cleaning properties, and low light transmittance to the cover glass of photovoltaic modules, resulting in low service life and photovoltaic power generation efficiency of photovoltaic modules. In order to solve this problem, this application provides a self-cleaning coating composition, a self-cleaning coating, and a method for preparing the same.

[0020] In a typical embodiment of this application, a self-cleaning coating composition is provided, comprising a carbon nanotube dispersion, a first nano-silica dispersion, a second nano-silica dispersion, and hexamethyldisilazane; wherein the first nano-silica dispersion comprises first nano-silica, the second nano-silica dispersion comprises second nano-silica, and the average particle size difference between the first nano-silica and the second nano-silica is 40-60 nm.

[0021] The self-cleaning coating composition provided by this invention utilizes two different particle sizes of hydrophobic nano-silica to create a suitable nano-roughness, while simultaneously increasing the porosity of the coating by adding a small amount of nanotubes. The roughness enhances the self-cleaning performance of the coating, while the micropore structure reduces light reflection and improves the light transmittance of the self-cleaning coating. For example, the self-cleaning coating of this invention achieves a maximum light transmittance of 90.1%, a maximum water contact angle of 161°, and a roll-off angle of less than or equal to 15°. Furthermore, the self-cleaning coating composition of this application uses inexpensive raw materials, is fluorine-free, and can be applied by spraying and dried at room temperature to form a film. The resulting coating has high transparency and excellent self-cleaning function, meeting the requirements for large-scale outdoor application.

[0022] In one embodiment of this application, the mass ratio of the first nano-silica to the second nano-silica is 1:2 to 2:1.

[0023] The preferred mass ratio of the first nano-silica to the second nano-silica helps to improve their synergistic effect, thereby giving the self-cleaning coating composition a more suitable nano-roughness.

[0024] In one embodiment of this application, the total mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 5 to 100:1, and / or the total mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 0.1 to 2.5:1.

[0025] The preferred mass ratio helps to improve the synergistic effect between the first nano-silica, the second nano-silica, the carbon nanotubes and hexamethyldisilazane, thereby making the self-cleaning coating composition more capable of achieving both good self-cleaning function and high light transmittance.

[0026] In one embodiment of this application, the carbon nanotube dispersion includes carbon nanotubes and a first dispersant; wherein the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes, preferably with a diameter of 2-30 nm; and / or the first dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0027] Carbon nanotubes are prone to self-aggregation. The preferred diameter of the carbon nanotubes and the first dispersant are within the above range, which helps to improve the dispersibility between carbon nanotubes in the carbon nanotube dispersion, thereby helping to improve the mixing uniformity of carbon nanotubes with the other components in the self-cleaning coating composition.

[0028] In one embodiment of this application, the first nano-silica dispersion further includes a second dispersant, wherein the average particle size of the first nano-silica is 5-50 nm; and / or the second dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0029] The first nano-silica itself is prone to self-aggregation. Preferably, the average particle size of the first nano-silica and the second dispersant are within the above range, which helps to improve the dispersibility of the first nano-silica in the first nano-silica dispersion, thereby helping to improve the mixing uniformity of the first nano-silica with the other components in the self-cleaning coating composition.

[0030] In one embodiment of this application, the second nano-silica dispersion further includes a third dispersant, wherein the average particle size of the second nano-silica is 51-100 nm; and / or the third dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

[0031] The second nano-silica itself is prone to self-aggregation. Preferably, the average particle size of the first nano-silica and the third dispersant are within the above range, which helps to improve the dispersibility of the second nano-silica in the second nano-silica dispersion, thereby helping to improve the mixing uniformity of the second nano-silica with the other components in the self-cleaning coating composition.

[0032] In another typical embodiment of this application, a method for preparing a self-cleaning coating is provided. The method includes step S1, mixing a self-cleaning coating composition by stirring to obtain a self-cleaning coating; and step S2, spraying the self-cleaning coating onto the surface of a substrate and then drying it to obtain a self-cleaning coating; wherein the self-cleaning coating composition is the aforementioned self-cleaning coating composition.

[0033] The preparation process of the self-cleaning coating described in this application is simple and inexpensive. The resulting self-cleaning coating utilizes two different sizes of hydrophobic nano-silica to create a suitable nano-roughness, while adding a small amount of nanotubes to increase the coating's porosity. The roughness enhances the coating's self-cleaning performance, while the micropore structure reduces light reflection and improves the coating's light transmittance. For example, the self-cleaning coating of this invention achieves a maximum light transmittance of 90%, a water contact angle of up to 161°, and a roll-off angle of less than or equal to 15°. Furthermore, the self-cleaning coating composition of this application uses inexpensive, fluorine-free raw materials. It can be applied by spraying and dried at room temperature to form a film. The resulting coating has high transparency and excellent self-cleaning function, meeting the requirements for large-scale outdoor application.

[0034] In one embodiment of this application, preferably in step S1, the stirring and mixing temperature is 20-30°C, and / or the stirring and mixing time is 0.5-48 h, and / or the stirring and mixing rate is 300-1000 rpm, thereby helping to obtain a self-cleaning coating with better uniformity. Preferably, step S1 also includes the preparation process of a first nano-silica dispersion and a second nano-silica dispersion, wherein the preparation process of the first nano-silica dispersion includes: mixing a first silicon source and a second dispersant to obtain a first mixture; heating the first mixture to 25-40°C and then adding ammonia water dropwise while stirring for 1-3 h; after the ammonia water dropwise addition is complete, continuing the stirring and reaction for 12-24 h to obtain the second nano-silica dispersion; wherein the volume ratio of the first silicon source to the second dispersant is 0.025-0.25:1; the volume ratio of ammonia water to the first silicon source is 0.5-1.5:1; and / or the preparation method of the second nano-silica dispersion includes: mixing the second silicon source with a third dispersant. Then, a second mixture is obtained; the second mixture is heated to 41-60°C and ammonia water is added dropwise while stirring for 1-3 hours. After the ammonia water is completely added, the stirring reaction continues for 12-24 hours to obtain a second nano-silica dispersion; wherein, the volume ratio of the second silicon source to the third dispersant is 0.025-0.25:1; the volume ratio of ammonia water to the second silicon source is 1.6-4:1; preferably, the first silicon source and the second silicon source are each independently selected from any one or more of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and methyltriethoxysilane (MTES); preferably, the total volume ratio of the first silicon source and the second silicon source to the volume ratio of hexamethyldisilazane is 0.1-10:1.

[0035] The preferred preparation process of the first nano-silica dispersion and the second nano-silica dispersion yields dispersions with better stability and uniformity.

[0036] In one embodiment of this application, in step S2 above, the drying temperature is 20-30°C, and / or the drying time is 3-48 hours; and / or the spraying pressure is 0.5-1 MPa, the spraying distance between the self-cleaning coating outlet and the substrate is 5-20 cm, preferably 8-15 cm, and the spraying time is preferably 1-3 seconds.

[0037] The preferred drying and spraying conditions, which are within the above range, are more conducive to improving the efficiency and effect of drying and spraying, and result in better uniformity of the final self-cleaning coating.

[0038] In yet another typical embodiment of this application, a self-cleaning coating is provided, which is prepared by the above-described preparation method.

[0039] The self-cleaning coating obtained by the method described in this application exhibits superior self-cleaning properties and light transmittance, thereby contributing to improved lifespan and photovoltaic power generation efficiency of photovoltaic modules. Furthermore, the raw materials for this self-cleaning coating are inexpensive, and the resulting coating after drying possesses high transparency and excellent self-cleaning capabilities, meeting the requirements for large-scale outdoor application.

[0040] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0041] Example 1

[0042] 1 mL of tetraethyl orthosilicate and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 30 °C, 1 mL of ammonia was slowly added dropwise and the mixture was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 40 nm.

[0043] 1 mL of tetraethyl orthosilicate and 25 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 50 °C, and 1.8 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 90 nm.

[0044] The average particle size difference between the first nano-silica and the second nano-silica is 50 nm, and the mass ratio of the first nano-silica to the second nano-silica is 1:1. After mixing the two dispersions, 0.1 g of single-walled carbon nanotubes and 10 mL of hexamethyldisilazane are added and stirred for 24 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 10 nm, the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the carbon nanotubes is 5.36:1, and the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the hexamethyldisilazane is 0.23:1.

[0045] The above coating was sprayed onto the glass surface at a pressure of 0.5 MPa, a distance of 10 cm, and a time of 2 seconds. After drying at room temperature for 5 hours, a superhydrophobic self-cleaning coating was obtained, with a maximum light transmittance of 90.0%, a water contact angle of 154°, and a roll-off angle of 5°.

[0046] Example 2

[0047] 1 mL of tetraethyl orthosilicate and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 30 °C, 1 mL of ammonia was slowly added dropwise and the mixture was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 40 nm.

[0048] 1 mL of hexadecyltrimethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 55 °C, and 2.0 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 98 nm.

[0049] The average particle size difference between the first nano-silica and the second nano-silica is 58 nm, and the mass ratio of the first nano-silica to the second nano-silica is 1.5:1. After mixing the two dispersions, 0.186 g of single-walled carbon nanotubes and 2 mL of hexamethyldisilazane are added and stirred for 12 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 25 nm, the mass ratio of the first nano-silica and the second nano-silica to the carbon nanotubes is 10:1, and the mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 1.16:1.

[0050] The above coating was sprayed onto the glass surface at a pressure of 0.5 MPa, a distance of 7 cm, and a time of 2 seconds. After drying at room temperature for 6 hours, a superhydrophobic self-cleaning coating was obtained, with a maximum light transmittance of 86.9%, a water contact angle of 153°, and a roll-off angle of 6°.

[0051] Example 3

[0052] 1.5 mL of tetraethyl orthosilicate and 30 mL of butyl acetate were added to the reaction vessel, and 2.1 mL of ammonia water was slowly added dropwise at room temperature and the mixture was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 50 nm.

[0053] 1.5 mL of methyltriethoxysilane and 25 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 50 °C, and 2.4 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 92 nm.

[0054] The average particle size difference between the first nano-silica and the second nano-silica is 42 nm, and the mass ratio of the first nano-silica to the second nano-silica is 1.04:1. After mixing the two dispersions, 0.1095 g of multi-walled carbon nanotubes and 9 mL of hexamethyldisilazane are added and stirred for 10 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 15 nm, the mass ratio of the first nano-silica and the second nano-silica to the carbon nanotubes is 25:1, and the mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 0.38:1.

[0055] The above coating was sprayed onto the glass surface at a pressure of 0.6 MPa, a distance of 18 cm, and a time of 3 seconds. After drying at room temperature for 4 hours, a superhydrophobic self-cleaning coating was obtained, with a maximum light transmittance of 86.3%, a water contact angle of 157°, and a roll-off angle of 5°.

[0056] Example 4

[0057] 3 mL of methyltriethoxysilane and 40 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 25 °C, and 1.6 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 20 nm.

[0058] 2 mL of methyltriethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 50 °C, 4 mL of ammonia water was slowly added dropwise and the mixture was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 65 nm.

[0059] The average particle size difference between the first nano-silica and the second nano-silica is 45 nm, and the mass ratio of the first nano-silica to the second nano-silica is 1.5:1. After mixing the two dispersions, 0.15 g of multi-walled carbon nanotubes and 20 mL of hexamethyldisilazane are added and stirred for 48 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 3 nm, the mass ratio of the first nano-silica and the second nano-silica to the carbon nanotubes is 30:1, and the mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 0.28:1.

[0060] The above coating was sprayed onto the glass surface at a pressure of 0.5 MPa, a distance of 10 cm, and a time of 2 seconds. After drying at room temperature for 5 hours, a superhydrophobic self-cleaning coating was obtained with a maximum light transmittance of 88.7%, a water contact angle of 158°, and a roll-off angle of 6°.

[0061] Example 5

[0062] 1.5 mL of hexadecyltrimethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 35 °C, and 1.5 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 35 nm.

[0063] 1.5 mL of methyltriethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 58 °C, and 2.5 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 83 nm.

[0064] The average particle size difference between the first nano-silica and the second nano-silica is 48 nm, and the mass ratio of the first nano-silica to the second nano-silica is 0.99:1. After mixing the two dispersions, 0.067 g of single-walled carbon nanotubes and 25 mL of hexamethyldisilazane are added and stirred for 20 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 10 nm, the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the carbon nanotubes is 40:1, and the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the hexamethyldisilazane is 0.1335:1.

[0065] The above coating was sprayed onto the glass surface at a pressure of 0.6 MPa, a distance of 8 cm, and a time of 3 seconds. After drying at room temperature for 7 hours, a superhydrophobic self-cleaning coating was obtained, exhibiting a maximum light transmittance of 84.1%, a water contact angle of 161°, and a roll-off angle of 3°. The water contact angle test photograph is shown below. Figure 1 As shown.

[0066] Example 6

[0067] 1.5 mL of methyltriethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 30 °C, 2 mL of ammonia water was slowly added dropwise and the mixture was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 64 nm.

[0068] 2 mL of tetraethyl orthosilicate and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 55 °C, and 8 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 110 nm.

[0069] The average particle size difference between the first nano-silica and the second nano-silica is 46 nm, and the mass ratio of the first nano-silica to the second nano-silica is 0.72:1. After mixing the two dispersions, 0.04 g of single-walled carbon nanotubes, 0.05 g of multi-walled carbon nanotubes, and 5 mL of hexamethyldisilazane are added and stirred for 1 h to obtain a self-cleaning coating. The diameter of the single-walled carbon nanotubes is 4 nm, the diameter of the multi-walled carbon nanotubes is 30 nm, the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the carbon nanotubes is 35.58:1, and the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of hexamethyldisilazane is 0.8:1.

[0070] The above coating was sprayed onto the glass surface at a pressure of 0.5 MPa, a distance of 15 cm, and a time of 1 second. After drying at room temperature for 5 hours, a superhydrophobic self-cleaning coating was obtained with a maximum light transmittance of 80.6%, a water contact angle of 152°, and a roll-off angle of 8°.

[0071] Example 7

[0072] 1 mL of hexadecyltrimethoxysilane and 30 mL of butyl acetate were added to the reaction vessel. 1 mL of ammonia was slowly added dropwise at room temperature and the mixture was stirred for 2 h. The reaction vessel was then left open at room temperature and stirred for 12 h. The average particle size of the first nano-silica obtained was 32 nm.

[0073] 1 mL of hexadecyltrimethoxysilane and 35 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 55 °C, 3 mL of ammonia water was slowly added dropwise and the reaction was stirred for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 85 nm.

[0074] The average particle size difference between the first nano-silica and the second nano-silica is 53 nm, and the mass ratio of the first nano-silica to the second nano-silica is 1:1. After mixing the two dispersions, 0.03 g of single-walled carbon nanotubes, 0.03 g of multi-walled carbon nanotubes, and 15 mL of hexamethyldisilazane are added and stirred for 6 h to obtain a self-cleaning coating. The diameter of the single-walled carbon nanotubes is 10 nm, the diameter of the multi-walled carbon nanotubes is 25 nm, the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of the carbon nanotubes is 29.5:1, and the mass ratio of the total mass of the first nano-silica and the second nano-silica to the mass of hexamethyldisilazane is 0.148:1.

[0075] The above coating was sprayed onto the glass surface at a pressure of 0.6 MPa, a distance of 6 cm, and a time of 2 seconds. After drying at room temperature for 4 hours, a superhydrophobic self-cleaning coating was obtained, with a maximum light transmittance of 87.5%, a water contact angle of 157°, and a roll-off angle of 5°.

[0076] Example 8

[0077] The difference from Example 5 is that the mass ratio of the first nano-silica to the second nano-silica is 1:2, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 89.6%, a water contact angle of 153°, and a roll-off angle of 5°.

[0078] Example 9

[0079] The difference from Example 5 is that the mass ratio of the first nano-silica to the second nano-silica is 2:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 88.3%, a water contact angle of 154°, and a roll-off angle of 6°.

[0080] Example 10

[0081] The difference from Example 5 is that the mass ratio of the first nano-silica to the second nano-silica is 3:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 80.6%, a water contact angle of 151°, and a roll-off angle of 10°.

[0082] Example 11

[0083] The difference from Example 5 is that the total mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 5:1, and the total mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 0.1:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 84.7%, a water contact angle of 153°, and a roll-off angle of 5°.

[0084] Example 12

[0085] The difference from Example 5 is that the total mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 100:1, and the total mass ratio of the first nano-silica and the second nano-silica to hexamethyldisilazane is 2.5:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 85.0%, a water contact angle of 168°, and a roll-off angle of 3°.

[0086] Example 13

[0087] The difference from Example 5 is that the total mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 4:1, and the total mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 3:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 80.5%, a water contact angle of 150°, and a roll-off angle of 15°.

[0088] Example 14

[0089] The difference from Example 5 is that the volume ratio of the first silicon source to the second dispersant is 0.025:1; the volume ratio of ammonia to the first silicon source is 0.5:1; the volume ratio of the second silicon source to the third dispersant is 0.025:1; the volume ratio of ammonia to the second silicon source is 1.6:1; and the volume ratio of the total volume of the first silicon source and the second silicon source to the volume of hexamethyldisilazane is 0.1:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 86.4%, a water contact angle of 157°, and a roll-off angle of 7°.

[0090] Example 15

[0091] The difference from Example 5 is that the volume ratio of the first silicon source to the second dispersant is 0.25:1; the volume ratio of ammonia to the first silicon source is 1.5:1; the volume ratio of the second silicon source to the third dispersant is 0.25:1; the volume ratio of ammonia to the second silicon source is 4:1; and the total volume ratio of the first silicon source and the second silicon source to the volume ratio of hexamethyldisilazane is 10:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 84.8%, a water contact angle of 159°, and a roll-off angle of 6°.

[0092] Example 16

[0093] The difference from Example 5 is that the volume ratio of the first silicon source to the second dispersant is 0.5:1; the volume ratio of ammonia to the first silicon source is 2:1; the volume ratio of the second silicon source to the third dispersant is 0.5:1; the volume ratio of ammonia to the second silicon source is 1:1; and the volume ratio of the total volume of the first silicon source and the second silicon source to the volume of hexamethyldisilazane is 0.05:1, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 80.9%, a water contact angle of 150°, and a roll-off angle of 13°.

[0094] Comparative Example 1

[0095] The difference from Example 1 is that 1 mL of tetraethyl orthosilicate and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 30°C, 1 mL of ammonia was slowly added dropwise and stirred for 2 hours, and then the reaction vessel was left open at room temperature and stirred for 12 hours. The average particle size of the first nano-silica obtained was 40 nm.

[0096] 1 mL of hexadecyltrimethoxysilane and 30 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 55 °C, and 0.5 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the second nano-silica obtained was 70 nm.

[0097] The average particle size difference between the first nano-sized silica and the second nano-sized silica is 30 nm, resulting in a superhydrophobic self-cleaning coating with a maximum light transmittance of 72.9%, a water contact angle of 125°, and a roll-off angle of 45°.

[0098] Comparative Example 2

[0099] 3 mL of tetraethyl orthosilicate and 60 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 50 °C, and 9 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the obtained nano-silica was 143 nm.

[0100] Add 0.08 g of single-walled carbon nanotubes and 9 mL of hexamethyldisilazane to the above dispersion and stir for 12 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 25 nm, the mass ratio of the total mass of nano-silica to carbon nanotubes is 34.875:1, and the mass ratio of the total mass of nano-silica to hexamethyldisilazane is 0.388:1.

[0101] The above coating was sprayed onto the glass surface at a pressure of 0.8 MPa, a distance of 12 cm, and a time of 2 seconds. After drying at room temperature for 10 hours, a superhydrophobic self-cleaning coating was obtained with a maximum light transmittance of 68.8%, a water contact angle of 113°, and a roll-off angle of 68°.

[0102] Comparative Example 3

[0103] 3 mL of tetraethyl orthosilicate and 60 mL of butyl acetate were added to the reaction vessel, the temperature was raised to 50 °C, and 3 mL of ammonia water was slowly added dropwise while stirring for 2 h. Then the reaction vessel was left open at room temperature and stirred for 12 h. The average particle size of the nano-silica was 78 nm.

[0104] Add 0.04 g of single-walled carbon nanotubes and 15 mL of hexamethyldisilazane to the above dispersion and stir for 2 h to obtain a self-cleaning coating. The diameter of the carbon nanotubes is 15 nm, the mass ratio of the total mass of nano-silica to the mass of carbon nanotubes is 70:1, and the mass ratio of the total mass of nano-silica to the mass of hexamethyldisilazane is 0.23:1.

[0105] The above coating was sprayed onto the glass surface at a pressure of 0.7 MPa, a distance of 10 cm, and a time of 2 seconds. After drying at room temperature for 8 hours, a superhydrophobic self-cleaning coating was obtained with a maximum light transmittance of 67.1%, a water contact angle of 110°, and a roll-off angle of 65°.

[0106] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0107] The self-cleaning coating composition provided by this invention utilizes two different particle sizes of hydrophobic nano-silica to create a suitable nano-roughness, while simultaneously increasing the porosity of the coating by adding a small amount of nanotubes. The roughness enhances the self-cleaning performance of the coating, while the micropore structure reduces light reflection and improves the light transmittance of the self-cleaning coating. For example, the self-cleaning coating of this invention achieves a maximum light transmittance of 90%, a water contact angle of up to 161°, and a roll-off angle of less than or equal to 15°. Furthermore, the self-cleaning coating composition of this application uses inexpensive raw materials, is fluorine-free, and can be applied by spraying and dried at room temperature to form a film. The resulting coating has high transparency and excellent self-cleaning function, meeting the requirements for large-scale outdoor application.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-cleaning coating composition, characterized in that, The self-cleaning coating composition comprises: Carbon nanotube dispersion; First nano-silica dispersion; Second nano-silica dispersion; and Hexamethyldisilazane; Wherein, the first nano-silica dispersion includes first nano-silica, the second nano-silica dispersion includes second nano-silica, the average particle size difference between the first nano-silica and the second nano-silica is 40~60nm; the average particle size of the first nano-silica is 20~50nm, and the average particle size of the second nano-silica is 51~100nm. The mass ratio of the first nano-silica to the second nano-silica is 1:2 to 2:1; The total mass ratio of the first nano-silica and the second nano-silica to the carbon nanotube is 5~100:1; the total mass ratio of the first nano-silica and the second nano-silica to the hexamethyldisilazane is 0.1~2.5:

1. The preparation process of the first nano-silica dispersion includes: mixing a first silicon source with a second dispersant to obtain a first mixture; heating the first mixture to 25~40℃ and then adding ammonia water dropwise while stirring for 1~3h; after the ammonia water dropwise addition is completed, continuing to stir for 12~24h to obtain the first nano-silica dispersion. The preparation method of the second nano-silica dispersion includes: mixing a second silicon source with a third dispersant to obtain a second mixture; heating the second mixture to 41~60℃ and then adding ammonia water dropwise while stirring for 1~3h; after the ammonia water dropwise addition is completed, continuing to stir for 12~24h to obtain the second nano-silica dispersion.

2. The self-cleaning coating composition according to claim 1, characterized in that, The carbon nanotube dispersion comprises carbon nanotubes and a first dispersant; wherein the carbon nanotubes are single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

3. The self-cleaning coating composition according to claim 2, characterized in that, The diameter of the carbon nanotubes is 2~30nm.

4. The self-cleaning coating composition according to claim 2, characterized in that, The first dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

5. The self-cleaning coating composition according to claim 1 or 2, characterized in that, The first nano-silica dispersion also includes a second dispersant.

6. The self-cleaning coating composition according to claim 5, characterized in that, The second dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

7. The self-cleaning coating composition according to claim 1 or 2, characterized in that, The second nano-silica dispersion also includes a third dispersant.

8. The self-cleaning coating composition according to claim 7, characterized in that, The third dispersant is selected from any one or more of butyl acetate, ethyl acetate, and ethylene glycol butyl ether.

9. A method for preparing a self-cleaning coating, the method comprising: Step S1: The self-cleaning coating composition is mixed by stirring to obtain a self-cleaning coating; Step S2: The self-cleaning coating is sprayed onto the surface of the substrate and then dried to obtain a self-cleaning coating. The self-cleaning coating composition is characterized in that it is the self-cleaning coating composition according to any one of claims 1 to 8.

10. The preparation method according to claim 9, characterized in that, In step S1, the stirring and mixing temperature is 20~30℃, and / or the stirring and mixing time is 0.5~48h, and / or the stirring and mixing rate is 300~1000rpm.

11. The preparation method according to claim 9, characterized in that, The volume ratio of the first silicon source to the second dispersant is 0.025~0.25:1; the volume ratio of ammonia water to the first silicon source is 0.5~1.5:

1.

12. The preparation method according to claim 9, characterized in that, The volume ratio of the second silicon source to the third dispersant is 0.025~0.25:1; the volume ratio of ammonia water to the second silicon source is 1.6~4:

1.

13. The preparation method according to claim 11, characterized in that, The first silicon source is selected from any one or more of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and methyltriethoxysilane (MTES).

14. The preparation method according to claim 12, characterized in that, The second silicon source is selected from any one or more of tetraethyl orthosilicate (TEOS), hexadecyltrimethoxysilane (HDTMS), and methyltriethoxysilane (MTES).

15. The preparation method according to claim 9, characterized in that, The total volume ratio of the first silicon source and the second silicon source to the volume ratio of the hexamethyldisilazane is 0.1 to 10:

1.

16. The preparation method according to claim 9, characterized in that, In step S2, the drying temperature is 20~30℃, and / or the drying time is 3~48h; and / or the spraying pressure is 0.5~1MPa, and the spraying distance between the self-cleaning coating outlet and the substrate is 5~20cm.

17. The preparation method according to claim 16, characterized in that, The spraying distance between the self-cleaning coating outlet and the substrate is 8-15cm.

18. The preparation method according to claim 16, characterized in that, The spraying time is 1~3 seconds.

19. A self-cleaning coating, characterized in that, The self-cleaning coating is prepared by the preparation method according to any one of claims 9 to 18.

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